1 - Wind in New Mexico can cause damage to newly formed leaves in the spring.
2 - A late freeze did indeed damage desert willows and other plants in parts of New Mexico this year.
Q.
Three years ago I planted a flowering pear tree. The last year or so the leaves have been curling with black edges. I am new to the southwest and must be doing something wrong as I have never had problems with trees before.
- Jessica
A.
There are several things that could cause the leaves to turn black, but your description that symptoms are along the edges of the leaves helps and the photographs confirm that you are probably seeing New Mexico spring wind damage. You did not tell where you are gardening, but the winds have been pretty strong over much of the state. Our spring winds often results in wind tearing the leaves and in bruising that can result in black areas on the leaves. Around the leaf margins this blackening may be due to bruising, but it may also be due to salt burn. Salt burn symptoms often appear at the leaf tip and along the leaf margins (edges). Soils in the Southwestern U.S. irrigation waters usually contain excess mineral salts that accumulate in plant leaves, especially along leaf margins. When winds dry the leaves, the burning due to surplus minerals becomes apparent as browning or blackening of the leaf margins.
There are diseases that could cause the symptoms you described. Fire blight is a bacterial disease spread by pollinators as they pollinate flowers. It common, but appears as a blackening of leaves and stems of new growth. They also exhibit a "shepherd's crook" shape to the blackened new growth. That is not what your pictures shows - that is good news. Disease is not your problem this year. The New Mexico spring winds are probably the cause of the problem you have described.
An update: Regarding Yard and Garden article the week of May 14 about desert willow trees not forming leaves properly. I received this information from Tom J. in Chaves County:
Regarding the column about damaged Desert Willow leaves - a late, hard freeze 3 - 4 weeks ago in SE NM caused significant frost burn / leaf damage to local Desert Willow, Mexican Elder and Gamble Oak trees. To be specific freezing temps on the weekend of 2 - 3 April 2016 hammered early vegetable gardens and bushes / trees relatively unprotected and exposed to wind out of the North as evidenced by leaf damage. We all should know about trying to get a step ahead of Mother Nature with an average last freeze date in Chaves County is the 15th of April...but that was the risk we took...
Thank you, Tom.
Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.
Links:
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